Method of converting functional group through halogen-metal exchange reaction

ABSTRACT

A method by which a halogen atom of a halogen compound can be efficiently replaced with an electrophilic group. 
     Also provided are: a reagent for converting a functional group through a halogen-metal exchange reaction, characterized by comprising either a mixture of a magnesium compound represented by the formula R 1 —Mg—X (I) (wherein R 1  represents a halogen atom or an optionally substituted hydrocarbon residue; and X 1  represents a halogen atom) and an organolithium compound represented by the formula R 2 —Li (II) (wherein R 2  represents an optionally substituted hydrocarbon residue) or a product of the reaction of the magnesium compound with the organolithium compound; and a process for producing with the reagent a compound in which a halogen atom of a halogen compound has been replaced with an electrophilic group.

This application is a 371 of PCT/JP01/00463 filed Jan. 24, 2001.

TECHNICAL FIELD

This invention is useful in the field of chemical industry. Moreparticularly, the present invention relates to a process for exchangingfunctional groups and to a reagent for halogen-metal exchange reaction,with industrial advantage, for a variety of useful compounds in thefields of chemical industry products, agrochemicals, andpharmaceuticals.

BACKGROUND ART

Halogen-metal exchange reaction is widely used as a technique forsubstituting a halogen atom present in a halogenated organic compoundinto other substituent. As a reagent employed in the halogen-metalexchange reaction are exemplified Grignard reagents and organolithiumreagents.

Since Grignard reagents have low reactivity in general, it is necessaryto often use such reagents in an excess when reacted with an arylchloride or an aryl bromide. Also, such reagents require a long reactiontime. Therefore, reaction with the Grignard reagents is of no practicaluse from standpoint of industrial production (see Tetrahedron Letters,Vol. 40, pages. 4339-4342 (1999) by F. Trecourt, et al.) On the otherhand, the Grignard reagents have a high reactivity for practical use toan aryl iodide, but it is troublesome to introduce an iodine atom in theway of synthetic route. The reaction using such Grignard reagents is,therefore, not desirable in view of industrial production (see Journalof Organic Chemistry, Vol. 57, pages 407-410 (1992) by Hisao Nishiyama,et al., Tetrahedron Letters Vol. 28, No. 47, pages 5845-5848 (1987) byNaomichi Furukawa, et al., and Journal of Organic Chemistry, Vol. 56,pages 5739-5740 (1991) by Richard M. Turner, et al.).

Organolithium reagents are widely used in halogen-metal exchangereaction, and can be also applied to a wide range of reactionsubstrates. However, thermostability of such organolithium compounditself or that of an intermediate lithio compound by-produced isgenerally not high. It is, therefore, essential to often carry out thereaction under the conditions of extreme low temperature which isunsuitable for industrial production (see. Journal of MedicinalChemistry, Vol. 42, pages 1088-1099, (1999) by Tatsuzo Ukita, et al.,Tetrahedron Letters, Vol. 37, No. 15, pages 2537-2540 (1996) by DongweiCai, et al., and Journal of Organic Chemistry, Vol. 58, pages 4382-4388(1993) by Jun'ichi Uenishi et al.).

Further, exchange reactions of functional groups in iodo alkenes (seeJournal of Organic Chemistry, Vol. 64, pages 1080-1081 (1999) by MarioRottlander, et al.) and in bromoaryl compounds or bromoheteroarylcompounds (see Tetrahedron letters, Vol. 40, pages 7449-7453 (1999) byMohamed Abarbri, et al.), using diisopropylmagnesium, are also known.

DISCLOSURE OF INVENTION

In the known methods as mentioned above, there is, however, restrictionin the reaction conditions which are unsuitable for industrialproduction, e.g. extreme low temperature and a narrow range of reactionsubstrates to be applied. Such drawbacks are required to be overcome. Itis, therefore, an object of the present invention to provide a processfor exchanging functional groups, which is applicable to industrialproduction of various useful compounds in a wide range of fields such aschemical industry products, agrochemicals or pharmaceuticals.

The present inventors have found that, as a result of diligent studiesof exchanging halogen atoms in organic compounds for electrophilicgroups, a halogen atom can be substituted with an electrophilic group inhigh yield at a low temperature of about 0° C. The substitution iscarried out by reacting a halogen atom attached to a carbon atom of adouble bond or attached to a carbon atom adjacent to the carbon atom ofthe triple bond in an organic compound having at least one carbon-carbondouble or triple bond, with a reaction product between a magnesiumcompound and an alkali metal compound, and reacting the resultantproduct with a compound having an electrophilic group, followed byoptional treatment with an acid. It has also been found that saidexchange of the halogen atom and said exchange reagent can be verywidely used in the field of industry. The present invention has beencompleted on the basis of these findings.

Namely, the present invention relates to an industrially useful reagentfor exchanging halogen atoms for functional groups by halogen-metalexchange reaction, wherein the reagent contains a mixture of a magnesiumcompound and an organolithium compound, or contains a reaction productthereof. The present invention is also directed to a process forsubstituting a halogen atom in a halogenated compound with anelectrophilic group by use of said reagent. More particularly, thepresent invention relates to

-   (1) an exchange reagent for a functional group by halogen-metal    exchange reaction, which comprises a mixture of (A) (1) a magnesium    compound represented by the formula:    R¹—Mg—X¹  (I)    (wherein R¹ is a halogen atom or an optionally substituted    hydrocarbon residue, and X¹ is a halogen atom) or (2) a member    selected from the group consisting of diethylmagnesium,    dipropylmagnesium, diisopropylmagnesium, di-n-butylmagnesium,    di-sec-butylmagnesium, di-tert-butylmagnesium, diphenylmagnesium,    divinylmagnesium, diallylmagnesium, di(2-furyl)magnesium,    di(3-furyl)magnesium, di(2-thienyl)magnesium, di(3-thienyl)magnesium    and dibenzylmagnesium and (B) an organolithium compound represented    by the formula:    R²—Li  (II)    (wherein R² is an optionally substituted hydrocarbon residue) or a    reaction product from (I) and (II).-   (2) the exchange reagent as described above in the item (1), wherein    the reaction product is

a compound of the formula III:(R^(a)R^(b)R^(c)Mg)⁻.Li⁺  (III)(wherein R^(a), R^(b) and R^(c) are same or differently an optionallysubstituted hydrocarbon residue), or

a compound of the formula IV:(R^(d)R^(e)R^(f)R^(g)Mg)²⁻.2Li⁺  (IV)(wherein R^(d), R^(e), R^(f) and R^(g) are same or differently anoptionally substituted hydrocarbon residue).

-   (3) the exchange reagent as described above in the item (2), wherein    R^(a), R^(b) and R^(c) are each n-butyl.-   (4) the exchange reagent as described in the item (2), wherein    R^(d), R^(e), R^(f) and R^(g) are each n-butyl.-   (5) an exchange process for exchanging a halogen atom present in a    halogenated compound for an electrophilic group, which comprises    reacting (i) a halogenated compound having in the molecule at least    one halogen atom or one double or triple bond to which is attached a    halogen-substituted carbon atom, with (ii) an exchange reagent as    described above in the item (1) or (2), reacting the resultant    product with (iii) a compound having an electrophilic group, and    optionally treating the resultant product with an acid.-   (6) the exchange process as described above in the item (5), wherein    the halogenated compound is a compound represented by the formula V:    (wherein Y¹ is a divalent organic residue, Y² is a monovalent    organic residue, or Y¹ and Y², when taken together, represent a    trivalent organic residue, X² is a halogen atom, and n¹ is 0 or 1)    or a compound represented by the formula VI:    A-(CH₂)_(n) ²—X³  (VI)    (wherein A is an optionally substituted aromatic ring, n² is 0 or 1,    and X³ is a halogen atom).-   (7) the exchange process as described above in the item (5), wherein    the halogenated compound is    (wherein X⁴ is a halogen atom, R³ is a hydrogen atom, a protected    amino group, an optionally substituted hydrocarbon group, an    optionally substituted hydrocarbon-oxy group or a halogen atom, and    n is 1 or 2).-   (8) the exchange process as described above in the item (5), wherein    the halogenated compound is a compound represented by the formula    VIII:    (wherein R⁴ is a hydrogen atom, a protected amino group, an    optionally substituted hydrocarbon group, an optionally substituted    hydrocarbon-oxy group or a halogen atom, and X⁵ is a halogen atom).-   (9) the exchange process as described above in the item (5), wherein    the compound having an electrophilic group is benzaldehyde,    chlorotrimethylsilane, or N,N-dimethylformamide.-   (10) the exchange process as described above in the item (5),    wherein the exchange reagent is an exchange reagent as described    above in the item (1), the magnesium compound represented by the    formula (I) as described above in the item (1) is n-butylmagnesium    bromide or n-butylmagnesium chloride, and the organolithium compound    represented by the formula (II) is n-butyllithium.-   (11) the exchange process as described above in the item (5),    wherein the reagent is an exchange reagent as described above in the    item(2), the compound represented by the formula (III) as described    above in the item (2) is tri-n-butylmagnesium lithium, and the    compound represented by the formula (IV) as described above in the    item (2) is tetra-n-butylmagnesium dilithium.-   (12) a mixture of (A) (1) a magnesium compound represented by the    formula:    R¹—Mg—X¹  (I)    (wherein R¹ is an optionally substituted hydrocarbon residue and X¹    is a halogen atom) or (2) a member selected from the group    consisting of diethylmagnesium, dipropylmagnesium,    diisopropylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium,    di-tert-butylmagnesium, diphenylmagnesium, divinylmagnesium,    diallylmagnesium, di(2-furyl)magnesium, di(3-furyl)magnesium,    di(2-thienyl)magnesium, di(3-thienyl)magnesium and dibenzylmagnesium    and (B) an organolithium compound represented by the formula:    R²—Li  (II)    (wherein R² is an optionally substituted hydrocarbon residue).-   (13) a process for preparing a compound wherein a halogen atom    present in a halogenated compound is substituted with an    electrophilic group, which comprises reacting (i) a halogenated    compound having in the molecule at least one halogen atom or one    double or triple bond to which is attached a halogen-substituted    carbon atom, with (ii) an exchange reagent as described above in the    item (1) or (2), reacting the resultant product with (iii) a    compound having an electrophilic group, and optionally treating the    resultant product with an acid, and-   (14) the exchange process as described above in the item (12) for    preparing 6-bromo-2-formylpyridine or a compound represented by the    formula:    (wherein R^(e) is a protected amino group), which comprises reacting    2,6-dibromopyridine or a compound represented by the formula:    (wherein R^(e) is a protected amino group), with a mixture of    n-butyl magnesium chloride and n-butyllithium or a reaction product    thereof, reacting the resultant product with N,N-dimethylformamide    and treating the resultant product with an acid.

The present reagent used for exchange reaction contains a mixture of amagnesium compound (I) represented by the formula:R¹—Mg—X¹  (I)(wherein R¹ is a halogen atom or an optionally substituted hydrocarbonresidue, and X¹ is a halogen atom) and an organolithium compound (II)represented by the formula:R²—Li  (II)(wherein R² is an optionally substituted hydrocarbon residue), orcontains a reaction product obtained from (I) and (II).

The halogen atoms represented by R¹ and X¹ in the above formulaeinclude, for example, chlorine, bromine, fluorine or iodine, among whichchlorine, bromine or iodine is preferable, and chlorine or bromine ismore preferable.

The hydrocarbon residues represented by R¹ and R² for optionallysubstituted hydrocarbon groups include, for example, linear or branchedaliphatic hydrocarbon groups and cyclic hydrocarbon groups, havingcarbon atoms of 1 to 20. More specifically, examples of said groups arealkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl or the like.

The alkyl groups include, for example, straight or branched C₁₋₁₂ alkylgroups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl or thelike, among which C₁₋₆ alkyl such as methyl, ethyl, propyl, isopropyl,butyl, isobutyl, sec-butyl, tert-butyl, or pentyl are preferable.

The alkenyl groups include, for example, C₂₋₆ alkenyl such as vinyl,allyl, isopropenyl, butenyl, isobutenyl, sec-butenyl or the like, amongwhich C₂₋₄ alkenyl such as vinyl, allyl, and isopropenyl are preferable.

The alkynyl groups include, for example, C₂₋₆ alkynyl such as propargyl,ethynyl, butynyl, 1-hexynyl or the like, among which propargyl, ethynylor butynyl is preferable.

The cycloalkyl groups include, for example, C₃₋₆ cycloalkyl such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or the like, which maybe fused or condensed with a benzene ring optionally substituted with 1to 3 lower alkoxy groups (e.g. C₁₋₆ alkoxy such as methoxy and the like)

The aryl groups include, for example, C₆₋₁₄ aryl such as phenyl,biphenylyl, naphthyl (e.g. 1-naphthyl or 2-naphthyl), indenyl (e.g.1-indenyl or 2-indenyl), anthlyl (e.g. 1-anthlyl, 2-anthlyl or3-anthlyl), phenanthlyl (e.g. 1-phenanthlyl, 2-phenanthlyl,3-phenanthyl, 4-phenanthlyl or 9-phenanthlyl), among which C₆₋₁₀ arylsuch as phenyl, 1-naphthyl or 2-naphthyl is more preferable.

The aralkyl groups include, for example, C₇₋₁₅ aralkyl such as benzyl,phenethyl, diphenylmethyl, 1-naphthylmethyl, 2-naphthylmethyl,2-phenylethyl, 2,2-diphenylethyl, 1-phenylpropyl, 2-phenylpropyl,3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl or the like, among whichC₇₋₁₃ aralkyl (e.g. benzyl) is preferable.

Among the hydrocarbon groups as mentioned above, C₁₋₆ alkyl ispreferable, and n-butyl or tert-butyl is particularly preferable.

The substituents of these hydrocarbon groups include, but are notlimited to, for example, (i) halogen (e.g. fluorine, chlorine, bromineor iodine), (ii) C₁₋₃ alkylenedioxy (e.g. methylenedioxy orethylenedioxy), (iii) nitro, (iv) cyano, (v) optionally halogenatedC₁₋₆alkyl (e.g. methyl, ethyl, n-propyl or trifluromethyl), (vi)optionally halogenated C₁₋₆ alkenyl (e.g. vinyl, allyl or isopropenyl),(vii) optionally halogenated C₁₋₆ alkynyl (e.g. propargyl, ethynyl,butynyl or 1-hexynyl), (viii) C₃₋₆ cycloalkyl optionally substituted byhalogen, C₁₋₃ alkylenedioxy, nitro, cyano or optionally halogenated C₁₋₆alkyl, (ix) optionally halogenated C₁₋₆ alkoxy, (x) optionallyhalogenated C₁₋₆ alkylthio, (xi) amino protected by known monovalent ordivalent amino-protecting groups such as phthaloyl,

said monovalent amino-protecting groups being, for example, benzyl,p-methoxybenzyl, p-nitrobenzyl, benzhydryl, formyl, acetyl, propionyl,phenylacetyl, phenoxyacetyl, pivaloyl, methoxycarbonyl, ethoxycarbonyl,isobutoxycarbonyl, t-butoxycarbonyl, 2-propenyloxycarbonyl,benzyloxycarbonyl or p-nitrobenzyloxycarbonyl), (xii) di-C₁₋₆ alkylamino(e.g. dimethylamino, dipropylamino or dibutylamino), (xiii)5- or6-membered cyclic amino (e.g. morpholino, thiomorpholino, piperidino orpyrrolidin-1-yl), (xiv) C₁₋₆ alkyl-carbonyl (e.g. acetyl or propionyl),(xv) C₁₋₆ alkoxy-carbonyl (e.g. methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl or butoxycarbonyl), (xvi) C₁₋₆ alkylsulfonyl (e.g.methylsulfonyl or ethylsulfonyl), (xvii) C₆₋₁₀ aryl (e.g. phenyl ornaphthyl) optionally substituted by halogen, C₁₋₃ alkylenedioxy, nitro,cyano or optionally halogenated C₁₋₆ alkyl, (xviii) C₇₋₁₅ aralkyl (e.g.benzyl, phenethyl, 2-phenylethyl, 1-phenylpropyl, 2-phenylpropyl ornaphthylmethyl) optionally substituted by halogen, C₁₋₃ alkylenedioxy,nitro, cyano or optionally halogenated C₁₋₆ alkyl, (xix) C₆₋₁₀ aryloxy(e.g. phenoxy or naphthyloxy) optionally substituted by halogen, C₁₋₃alkylenedioxy, nitro, cyano or optionally halogenated C₁₋₆ alkyl, (xx)C₇₋₁₆ aralkyloxy (e.g. benzyloxy) optionally substituted by halogen,C₁₋₃ alkylenedioxy, nitro, cyano or optionally halogenated C₁₋₆ alkyl,(xxi) oxo, (xxii) di-C₁₋₆ alkyl-thiocarbamoyl (e.g.dimethylthiocarbamoyl or diethylthiocarbamoyl), (xxiii) C₆₋₁₀aryl-carbonyloxy (e.g. phenylcarbonyloxy), (xxiv) C₆₋₁₄ arylsulfonamide(e.g. phenylsulfonamide), and (xxv) C₁₋₆ alkylsulfonamide (e.g.methylsulfonamide or ethylsulfonamide).

The magnesium compound (I) can be preferably a compound represented bythe formula:R^(1′)—Mg—X¹  (I′)(wherein R^(1′) is a halogen atom, C₁₋₁₂ alkyl, C₂₋₄ alkenyl, C₆₋₁₀ arylor C₇₋₁₃ aralkyl, and X¹ is a halogen atom)

Examples of C₁₋₁₂ alkyl, C₂₋₄ alkenyl, C₆₋₁₀ aryl or C₇₋₁₃ aralkylrepresented by R^(1′) are the same as those defined above for thehydrocarbon groups represented by R¹.

Examples of the halogen atoms represented by R^(1′) and X¹ are the sameas those defined above for R¹ and X.

Typically the magnesium compounds (I) include, for example, magnesiumbromide, magnesium iodide, magnesium chloride, magnesium fluoride,dimethylmagnesium iodide, methylmagnesium chloride, methylmagnesiumiodide, methylmagnesium chloride, methylmagnesium iodide,diethylmagnesium, ethylmagnesium chloride, ethylmagnesium bromide,ethylmagnesium iodide, dipropylmagnesium, propylmagnesium chloride,propylmagnesium bromide, propylmagnesium iodide, diisopropylmagnesium,isopropylmagnesium chloride, isopropylmagnesium bromide,isopropylmagnesium iodide, di-n-butylmagnesium, n-butylmagnesiumchloride, n-butylmagnesium bromide, n-butylmagnesium iodide,di-sec-butylmagnesium, sec-butylmagnesium chloride, sec-butylmagnesiumbromide, sec-butylmagnesium iodide, di-tert-butylmagnesium,tert-butylmagnesium chloride, tert-butylmagnesium bromide,tert-butylmagnesium iodide, diphenylmagnesium, phenylmagnesium chloride,phenylmagnesium bromide, phenylmagnesium iodide, divinylmagnesium,vinylmagnesium chloride, vinylmagnesium bromide, vinylmagnesium iodide,diallylmagnesium, allylmagnesium chloride, allylmagnesium bromide,allylmagnesium iodide, di(2-furyl)magnesium, 2-furylmagnesium chloride,2-furylmagnesium bromide, 2-furylmagnesium iodide, di(3-furyl)magnesium,3-furylmagnesium chloride, 3-furylmagnesium bromide, 3-furylmagnesiumiodide, di(2-thienyl)magnesium, 2-thienylmagnesium chloride,2-thienylmagnesium bromide, 2-thienylmagnesium iodide,di(3-thienyl)magnesium, 3-thienylmagnesium chloride, 3-thienylmagnesiumbromide, 3-thienylmagnesium iodide, dibenzylmagnesium, benzylmagnesiumchloride, benzylmagnesium bromide or benzylmagnesium iodide, among whichn-butyl magnesium or n-butylmagnesium is especially preferable.

The organolithium compound (II) can be preferably a compound representedby the formula:R^(2′)—Li  (II′)(wherein R^(2′) is C₁₋₁₂ alkyl, C₂₋₄ alkenyl, C₆₋₁₀ aryl or C₇₋₁₃aralkyl).

The C₁₋₁₂ alkyl, C₂₋₄ alkenyl, C₆₋₁₀ aryl and C₇₋₁₃ aralkyl groupsrepresented by R^(2′) are the same as those except for the halogen atomin the definition of R^(1′) described above.

Typically, the organolithium compounds (II) include, for example,ethyllithium, propyllithium, n-butyllithium, sec-butyllithium,isobutyllithium, tert-butyllithium, methyllithium, 2-furyllithium,vinyllithium, allyllithium, benzyllithium, 2-thienyllithium orphenyllithium, among which n-butyllithium is particularly preferred.

The mixture of magnesium compound (I) and organolithium compound (II)can be prepared by mixing the two compounds together in an arbitraryproportion. It is preferred to add about one to four moles of theorganolithium compound (II) per mole of the magnesium compound (I).Examples of the reaction products from the magnesium compound (I) andthe organilithium compound (II) are a compound represented by theformula:(R^(a)R^(b)R^(c)Mg)²⁻.Li⁺  (III)(wherein R^(a), R^(b), and R^(c) are the same or different and are eacha hydrocarbon residue which may be substituted) and a compoundrepresented by the formula:(R^(d)R^(e)R^(f)R^(g)Mg)²⁻.2Li⁺  (IV)(wherein R^(d), R^(e), R^(f), and R^(g) are the same or different andare each a hydrocarbon residue which may be substituted).

In the above formulae, examples of the optionally substitutedhydrocarbon residues represented by R^(a), R^(b), R^(c), R^(d), R^(e),R^(f), and R^(g) are the same as those defined above for R¹ and R²,among which C₁₋₆ alkyl, particularly n-butyl, is preferred.

Typically tri-n-butylmagnesium lithium or the like is preferably used asthe compound (III).

As the compound (IV) is preferably used tetra-n-butyl-magnesiumdilithium or the like.

The magnesium compounds (I), the organolithium compounds (II), and amixture of (I) and (II) can be prepared according to per se knownmethods.

The mixture of the magnesium compounds (I) and the organolithiumcompounds (II) are novel.

The reaction product from the magnesium compound (I) and theorganolithium compound (II) can be, for example, prepared by allowingboth compounds to react in an inert solvent.

The inert solvent used in the present reaction can be any solvents usedin halogen-metal exchange reaction with Grignard reagents andorganolithium compounds. Typically, toluene, xylene, tetrahydrofuran,diethyl ether, dimethoxyethane or a mixture thereof is preferably used.

The magnesium compound (I) is usually used in approximately 0.25 to 1.0molar equivalent to the organolithium compound (II).

The reaction temperature is usually about −10° C. to room temperature,preferably about −10° C. to 0° C.

The reaction time is usually about 5 minutes to 2 hours, preferablyabout 15 minutes to one hour.

The mixture of the compound (I) and the organolithium compound (II) ortheir reaction product, thus obtained in the present invention, isisolated and purified, or may be served without isolation as an exchangereagent for the functional groups in the halogen-metal exchange reactionas hereinafter described.

By use of the present exchange reagents, the halogen-metal exchangereaction can be effected under milder conditions, i.e., at about −10° C.to room temperature (about 10° C. to 40° C.), different from extreme lowtemperature.

The substitution process of the present invention relates to a processfor substituting a halogen atom present in halogenated compounds with anelectrophilic group, which comprises reacting (i) a halogenated compoundhaving in the molecule at least one halogen atom or one double or triplebond to which is attached a halogen-substituted carbon atom, with (ii)an exchange reagent as hereinbefore described, reacting the resultantproduct with (iii) a compound having an electrophilic group, andoptionally hydrolyzing the resultant product.

The term “a halogenated compound having in the molecule at least onehalogen atom or one double or triple bond” means starting materialsemployed in the halogen-metal exchange reaction, such as Grignardreagents and/or organolithium compounds.

These halogenated compounds are exemplified by

(1) a compound of the formula:

(wherein Y¹ is a divalent organic residue, Y² is a monovalent organicresidue, or Y¹ and Y², taken together, may form a trivalent organicresidue, X² is a halogen atom, and n¹ is 0 or 1),

(2) a compound of the formula:A-(CH₂)_(n) ²—X³  (VI)(wherein A is an optionally substituted aromatic ring, n² is 0 or 1, andX³ is a halogen atom),

(3) a compound of the formulae:

(wherein X⁴ is a halogen atom, R³ is a hydrogen atom, a protected aminogroup, an optionally substituted hydrocarbon group, an optionallysubstituted hydrocarbon-oxy group or a halogen atom and n is 1 or 2),and

(4) a compound of the formula:

(wherein R⁴ is a hydrogen atom, a protected amino group, an optionallysubstituted hydrocarbon group, an optionally substituted hydrocarbon-oxygroup or a halogen atom, and X⁵ is a halogen atom).

The halogen atoms represented by X², X³, X⁴, X⁵, R³ and R⁴ are the sameas those defined above for X¹, among which bromine is preferable.

The optionally substituted hydrocarbon groups represented by R³ and R⁴are the same as those defined above for R¹ which is an optionallysubstituted hydrocarbon group.

The optionally substituted hydrocarbon-oxy groups can be a grouprepresented by the formula: —OR⁵ (R⁵ is an optionally substitutedhydrocarbon group). The optionally substituted hydrocarbon groupsrepresented by R⁵ are the same as those defined above for R¹.

The protected amino groups represented by R³ and R⁴ are the same asthose described above for (xii) as a substituent of R¹which is anoptionally substituted hydrocarbon group.

The divalent organic groups represented by Y¹ can be an organic residuewhich is capable of attaching to the adjacent carbon atom via a doublebond, and include, for example,

(1) a group represented by the formula:Y³—CR^(f)═(wherein Y³ is a hydrogen atom, an optionally substituted hydrocarbongroup or an optionally substituted heterocyclic group, R^(f) is ahydrogen atom or a C₁₋₆ alkyl group (e.g. methyl, ethyl, propyl orn-butyl) and

(2) a group represented by the formula:

(wherein Y⁴ is an optionally substituted 3- to 8-membered carbocyclicgroup).

The optionally substituted hydrocarbon groups represented by Y³ are thesame as those described above for R¹ which is an optionally substitutedhydrocarbon group, among which optionally halogenated C₁₋₆ alkyl (e.g.methyl, ethyl) or optionally halogenated C₂₋₆ alkenyl (e.g. ethenyl,propenyl) are preferred, and particularly C₁₋₆ alkyl is preferable.

The optionally substituted heterocycles represented by Y³ can be, forexample, 5- to 8-membered monocyclic non-aromatic heterocycles,monocyclic aromatic heterocycles, or benzene-fused or naphthalene-fusedaromatic heterocycles, containing one or more hetero atoms (e.g. one tofour hetero atoms, preferably one to three hetero atoms) selected fromnitrogen, sulfur and oxygen other than carbon. Typically suchheterocycles include, for example, pyrrolidine, piperidine, piperazine,morpholine, thiophene, benzo(b)thiophene, benzo(b)furan, benzimidazole,benzoxazole, benzothiazole, benzisothiazole, naphth(2,3-b)thiophene,thianthrene, furan, isoindolizine, xanthlene, phenoxathiin, pyrrole,imidazole, triazole, thiazole, oxazole, pyrazole, pyridine, pyrazine,pyrimidine, pyridazine, indole, isoindole, 1H-indazole, purine,4H-quinolizine, isoquinoline, quinoline, phthalazine, naphthyridine,quinoxaline, quinazoline, cinnoline, carbazole, β-carboline,phenanthridine, acridine, phenazine, isothiazole, phenothiazine,isoxazole, furazane, phenoxazine, isochromane, or so forth, among whicha monovalent group formed by removing one hydrogen atom in the ring ofpyridine, thiophene or furan is preferred, and pyridyl, furyl, orthiazolyl are particularly preferable.

Among the optionally substituted heterocyclic groups represented by Y³as exemplified above, the NH group, if present, in the heterocyclic ringof pyrrolidine, piperidine, piperazine, morpholine, benzimidazole,isoindolizine, imidazole, triazole, pyrazole, indole, isoindole,1H-indazole, purine, carbazole, β-carboline, phenothiazine orphenoxazine is protected by known amino-protecting groups (e.g. benzyl).

The substituents of these heterocycles are the same as those of theoptionally substituted hydrocarbon groups represented by R¹ as describedabove.

R^(f) is preferably a hydrogen atom.

The 3- to 8-membered carbocyclic groups represented by Y⁴ areexemplified by 3- to 8-membered saturated carbocycles or 3- to8-membered unsaturated carbocycles, and include, for example, 3- to8-membered cycloalkanes (e.g. cyclopropane, cyclobutane, cyclopentane,cyclohexane, cycloheptane, cyclooctane), cycloalkenes (e.g. cyclobutene,cyclopentene, cyclohexene, cycloheptene, cyclooctene),cycloalkane-dienes (e.g. cycloheptane-diene, cyclohexane-diene,cycloheptane-diene, cyclooctane-diene), among which 5- to 7-memberedcycloalkanes (e.g. cyclopentane, cyclohexane, cycloheptane) arepreferred.

Typically a group represented by the formula: includes preferably, forexample,

Examples of the substituents on the 3- to 7-membered carbocycles arehalogen (e.g. fluorine, chlorine or bromine), hydroxyl, carboxy, or C₁₋₆alkoxy-carbonyl (e.g. acetoxy or ethoxycarbonyl).

The monovalent organic residue represented by Y² is a group formed byremoving one arbitrary hydrogen atom from an organic group. Examples ofsuch groups are an optionally substituted hydrocarbon group, anoptionally substituted heterocyclic group, a group represented by theformula: —NY⁵Y⁶ (wherein Y⁵ and Y⁶ are independently an optionallysubstituted hydrocarbon group, an optionally substituted heterocyclicgroup and an acyl group), a group represented by the formula: —O—Y⁷(wherein Y⁷ is a hydrogen atom, an optionally substituted hydrocarbongroup or an optionally substituted heterocyclic group) or a grouprepresented by the formula: —S—Y⁸ (wherein Y⁸ is a hydrogen atom, anoptionally substituted hydrocarbon group or an optionally substitutedheterocyclic group).

The optionally substituted hydrocarbon groups represented by Y², Y⁵, Y⁶,Y⁷ and Y⁸ are the same as those defined above for R¹ which is anoptionally substituted hydrocarbon group, among which C₁₋₆alkyl groups(e.g. methyl or ethyl) which may be halogenated are preferred.

The optionally substituted heterocyclic groups represented by Y², Y⁵,Y⁶, Y⁷ and Y⁸ are the same as those defined above for Y³ which is anoptionally substituted heterocyclic group.

The acyl groups represented by Y⁵ and Y⁶ can be a group represented bythe formula: —CO—Y⁹ wherein Y⁹ is an optionally substituted hydrocarbongroup. The optionally substituted hydrocarbon groups represented by Y⁹are the same as those defined above for R¹ which is an optionallysubstituted hydrocarbon group, among which C₁₋₆ alkyl groups (e.g.methyl, ethyl) which may be halogenated are preferred.

The trivalent organic residues formed when Y¹ and Y² are taken together,and represented by the formula:

are, for example,

R⁹ is a known amino-protecting group such as benzyl or the like.

Examples of the aromatic rings in the optionally substituted aromaticrings are aromatic hydrocarbon groups or aromatic heterocyclic groups.

The aromatic hydrocarbon groups include monocyclic, fused polycyclic, orpolycondensed aromatic hydrocarbons, having 6 to 14 carbon atoms.Typical examples of such aromatic hydrocarbons are C₆₋₁₄ aryl, includingphenyl, biphenylyl, naphthyl (e.g. 1-naphthyl or 2-naphthyl), indenyl(e.g. 2-indenyl), anthlyl (e.g. 1-anthlyl, 2-anthlyl or 3-anthlyl) orphenanthlyl (e.g. 1-phenanthlyl, 2-phenanthlyl, 3-phenanthlyl,4-phenanthlyl or 9-phenanthlyl), among which phenyl, biphenylyl,1-naphthyl, 2-naphthyl or the like are preferable, and phenyl isparticularly preferable.

The aromatic heterocyclic groups can be, for example, 5- to 8-memberedmonocyclic aromatic heterocycles, or benzene-fused or naphthalene-fusedaromatic heterocycles, containing one or more hetero atoms (e.g. one tofour hetero atoms, preferably one to three hetero atoms) selected fromnitrogen, sulfur and oxygen other than carbon. Typically suchheterocycles include, for example, thiophene, benzo(b)thiophene,benzo(b)furan, benzimidazole, benzoxazole, benzothiazole,benzisothiazole, benzisothiazole, naphth(2,3-b)thiophene, thianthrene,furan, isoindolizine, xanthlene, phenoxathiin, pyrrole, imidazole,triazole, thiazole, oxazole, pyrazole, pyridine, pyrazine, pyrimidine,pyridazine, indole, isoindole, 1H-indazole, purine, 4H-quinolizine,isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline,quinazoline, cinnoline, carbazole, β-carboline, phenanthridine,acridine, phenazine, isothiazole, phenothiazine, isoxazole, furazane,phenoxazine, isochromane, or a monovalent group formed by removing onehydrogen atom from the rings fused with one or more (preferably one totwo, especially one) benzene or naphthyl rings, among which pyridyl,pyrimidinyl, pyrazinyl or furyl is preferred.

Among the aromatic heterocycles as exemplified above, the NH group, ifany, on the heterocyclic ring such as benzimidazole, isoindolizine,pyrrole, imidazole, triazole, pyrazole, indole, isoindole, 1H-indazole,purine, carbazole, β-carboline, phenothiazine or phenoxazine isprotected by known amino-protecting groups (e.g. benzyl).

The substituents of these aromatic groups are the same as those of thehydrocarbon groups described above for R¹.

Among others as described above, the symbol “A” can be preferably 5- to8-membered monocyclic aromatic heterocycles containing one to threehetero atoms selected from nitrogen, sulfur and oxygen other thancarbon. In particular, pyridyl, pyrimidinyl, pyrazinyl or furyl ispreferred.

As the compound (V) is preferred a compound when Y¹ is (i) a group ofthe formula: Y^(3′)—CH═(wherein Y^(3′) is C₁₋₆ alkyl) or (ii) a group ofthe formula:

(wherein Y^(4′) is a 3- to 8-membered cycloalkane), Y² is C₁₋₆ alkyl, n¹is 0 or 1, and X² is chlorine or bromine.

As the compound (VI) is preferred a compound when A is phenyl, pyrazylor furyl, all these being optionally substituted by halogen, halogenatedC₁₋₆ alkyl or optionally halogenated C₁₋₆ alkoxy, n² is 0 or 1, and X³is chlorine or bromine.

As the compound (VII) is preferred a compound when R³ is amino protectedby, for example, pivaloyl, benzyl, phthaloyl or t-butoxycarbonyl,halogen (e.g. chlorine or bromine), C₁₋₆ alkyl or C₁₋₆ alkoxy, and X⁴ ischlorine or bromine.

As the compound (VIII) is preferred a compound when R⁴ is aminoprotected by, for example, pivaloyl, benzyl, phthaloyl ort-butoxycarbonyl, halogen (e.g. chlorine or bromine), C₁₋₆ alkyl or C₁₋₆alkoxy, and X⁴ is chlorine or bromine.

Among the halogenated compounds as described above is preferred acompound represented by the formula (VIII). Particularly,2,6-dibromopyridine or a compound represented by the formula:

(wherein R^(h) is an amino group protected by pivaloyl, benzyl,phthaloyl or t-butoxycarbonyl) are preferred.

The aforementioned reagents for exchange reaction of the presentinvention can be employed as an exchange reagent.

In particular, the magnesium compounds include preferablyn-butylmagnesium bromide and n-butylmagnesium chloride, and theorganolithium compounds include preferably n-butyl-lithium.

As the compound (III) is preferred tri-n-butylmagnesium lithium, and asthe compound (IV) is preferable, for example, tetra-n-butylmagnesiumdilithium.

The compounds having an electrophilic group can be any kind of moleculescapable of accepting an electron, preferably compounds with highelectron density capable of reacting with lone electron pair. Since theexchange reaction of the present invention is an improved halogen-metalexchange reaction with Grignard reagents and/or organolithium reagents,the aforementioned electrophilic compounds mean any electrophilicreagents employed for the halogen-metal exchange reaction, such asGrignard reagents and/or organolithium compounds.

Typically the compounds having an electrophilic group include, forexample, halogen (e.g. chlorine, bromine or iodine), carbon dioxide,solid sulfur, sulfur dioxide, oxygen or compounds represented by theformulae (1) to (21) given below.

The definitions of symbols in the formulae (1) to (21) are as follows:

The term “C₅₋₁₂aryl” means, for example, cyclopentadienyl, phenyl,indenyl, biphenylyl or naphthyl, among which phenyl is preferred.

The term “C₁₋₁₂ alkyl” means, for example, a linear or branched alkylgroup such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl orthe like, among which methyl, ethyl, propyl, isopropyl, butyl, butyl,pentyl, decyl, dodecyl or the like are preferable, and methyl, ethyl,propyl, butyl, hexyl or dodecyl is particularly preferred.

The term “C₁₋₄ alkyl” means, for example, a linear or branched alkylgroup such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl ort-butyl, among which methyl, ethyl, propyl, isopropyl or butyl ispreferable, and methyl, ethyl, propyl, or butyl is particularlypreferable.

The term “C₂₋₄ alkenyl” means, for example, a linear alkenyl group suchas vinyl, allyl, 1-butenyl or 2-butenyl, among which vinyl or allyl ispreferable.

The term “C₆₋₁₀ aryl” means, for example, an aryl group such as phenyl,o-tolyl, m-tolyl, p-tolyl, o-anisyl, m-anisyl, p-anisyl, 1-naphthyl or2-naphthyl, among which phenyl, p-tolyl, p-anisyl or 2-naphthyl ispreferable.

The term “C₆₋₁₀ arylthio” means, for example, an arylthio group such asphenylthio, o-tolylthio, m-tolylthio, p-tolylthio, o-anisylthio,m-anisylthio, p-anisylthio, 1-naphthylthio or 2-naphthylthio, amongwhich phenylthio, p-tolylthio, p-anisylthio or 2-naphthylthio ispreferable.

The term “C₇₋₁₃ aralkyl” means, for example, an aralkyl group such asbenzyl, o-tolylmethyl, m-tolylmethyl, p-tolylmethyl, o-anisylmethyl,m-anisylmethyl, p-anisylmethyl, benzhydryl, 1-naphthylmethyl or2-naphthylmethyl, among which benzyl, p-tolylmethyl, p-anisylmethyl or2-naphthylmethyl is preferable.

The term “C₄₋₈ heteroaryl” means, for example, a heteroaryl group suchas 2-thienyl, 3-thienyl, 2-furyl, 3-furyl, benzofuranyl or benzothienyl,among which 2-thienyl, 3-thienyl, 2-furyl or 3-furyl is preferable.

The term “C₁₋₄ alkoxy” means, for example, a linear or branched alkoxygroup such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy ortert-butoxy, among which methoxy, ethoxy, propoxy or butoxy ispreferable, and in particular methoxy, ethoxy or butoxy is preferred.

The term “C₂₋₅ alkoxycarbonylamino” means, for example, a linear orbranched alkoxy group such as methoxcycarbonylamino,ethoxycarbonylamino, propoxycarbonylamino, isopropoxycarbonylamino,butoxycarbonylamino, isobutoxycarbonylamino or t-butoxycarbonylamino,among which methoxcycarbonylamino, ethoxycarbonylamino,propoxycarbonylamino, or butoxycarbonylamino is preferable, andmethoxcycarbonylamino, ethoxycarbonylamino, or butoxycarbonylamino isparticularly preferred.

The term “C₁₋₄ alkylthio” means, for example, a linear or branchedalkylthio group such as methylthio, ethylthio, propylthio, isobutylthio,butylthio, isobutylthio or t-butylthio, among which methylthio,ethylthio, propylthio, and butylthio are preferable, and methylthio,ethylthio or butylthio is particularly preferred.

The term “C₁₋₄ alkylamino” means, for example, a linear or branchedalkylamino group such as methylamino, ethylamino, propylamino,isopropylaminoi, butylamino, isobutylamino or t-butylamino, among whichmethylamino, ethylamino, propylamino, butylamino, isobutylamino ort-butylamino is preferable, and methylamino, ethylamino or butylamino isparticularly preferred.

The term “N,N-di-C₁₋₄ alkylamino” means, for example, a di-linear orbranched alkylamino group such as dimethylamino, diethylamino,dipropylamino, diisopropylamino, dibutylamino, diisobutylamino ordi-t-butylamino, among which dimethylamino, diethylamino, dipropylamino,dibutylamino, diisobutylamino or di-t-butylamino is preferable, anddimethylamino, diethylamino, or dibutylamino is particularly preferable.

The term “C₅₋₁₂ aryl” means, for example, cyclopentadienyl, phenyl,indenyl, biphenylyl and naphthyl, among which phenyl is preferable.

The term “C₄₋₁₀ heterocyclic group” means a heteroycle which contains,as a hetero atom, one to four groups selected from oxygen, a group ofthe formula: S(→O)_(n) ³(n³ is 0, 1 or 2), a group of the formula: N→O,a group of the formula: ═N— and a group of the formula: NR⁵ (R⁵ is C₁₋₄alkyl or benzyl), such as furyl, thienyl, 1-benzylpyrrol,1-benzylimidazolyl, quinolyl, isoquinolyl, pyridyl, indolyl, pyrimidinylor piperazinyl, among which furyl, thienyl, 1-benzylpyrrol,1-benzylimidazolyl, quinolyl, isoquinolyl, or pyridyl is preferred.

The term “C₇₋₁₃ aralkyl” means, for example, an aralkyl group such asbenzyl, phenethyl, indenylmethyl, biphenylylmethyl or naphthylmethyl,among which benzyl and naphthylmethyl is preferable.

The term “C₁₋₄ alkylsulfonyl” means, for example, a linear or branchedalkylsulfonyl group such as methylsulfonyl, ethylsulfonyl,propylsulfonyl, isopropylsulfonyl, butylsulfonyl, isobutylsulfonyl andt-butylsulfonyl, among which methylsulfonyl, ethylsulfonyl,propylsulfonyl, butylsulfonyl or t-butylsulfonyl is preferable, andmethylsulfonyl, ethylsulfonyl or butylsulfonyl is particularlypreferred.

The term “C₁₋₅ alkanoyl” means, for example, a linear or branchedalkanoyl such as acetyl, propionyl, butyryl, isobutyryl, valeryl orpivaloyl, among which acetyl, butyryl, isobutyryl or pivaloyl ispreferable, and acetyl, butyryl, or pivaloyl is particularly preferred.

The term “C₁₋₅ alkoxycarbonyl” means, for example, a linear or branchedalkoxycarbonyl group such as methoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonylor t-butoxycarbonyl, among which ethoxycarbonyl, propoxycarbonyl,butoxycarbonyl or t-butoxycarbonyl is preferable, and ethoxycarbonyl,butoxycarbonyl or t-butoxycarbonyl is particularly preferred.

The term “C₃₋₁₂ alkylene” means, for example, a linear alkylene groupsuch as trimethylene, tetramethylene, pentamethylene, hexamethylene,heptamethylene, octamethylene, nonamethylene, decamethylene,undecamethylene or dodecamethylene, among which trimethylene,tetramethylene, pentamethylene, nonamethylene, decamethylene,undecamethylene or dodecamethylene is preferable, and trimethylene,tetramethylene, decamethylene, undecamethylene or dodecamethylene isparticularly preferred.

The term “C₄₋₇ alkylene” means, for example, a linear alkylene groupsuch as tetramethylene, pentamethylene, hexamethylene or heptamethylene,among which tetramethylene, pentamethylene or hexamethylene ispreferable, and tetramethylene or pentamethylene is particularlypreferred.

-   (1) A compound represented by the formula:    (wherein R⁶ and R⁷ are independently hydrogen, C₁₋₄ alkyl, halogen,    C₁₋₄ lower alkoxy, C₁₋₄ alkylthio, C₆₋₁₀ arylthio, N,N-di-C₁₋₄    alkylamino, C₅₋₁₂ aryl, or C₄₋₁₀ heterocycle (optionally containing    one to four hetero atoms selected from oxygen, a group of the    formula: S(→O)_(n) ⁴ (n⁴ is 0, 1 or 2), a group of the formula: N→O,    a group of the formula: ═N—, or a group of the formula: NR⁸ (R⁸ is    C₁₋₄ alkyl or benzyl)).

Typical examples of compounds (1) used are N,N-dimethylformamide, ethylformate, N,N-dimethylaminocarbonyl chloride, N,N-dimethylacetamide,acetyl chloride, ethyl benzoate, diethyl carbonate, ethylchlorocarbonate, benzophenone, benzaldehyde, ethyl chlorothiocarbonate,and the like.

-   (2) An acid anhydride represented by the formula:    (wherein R⁹ and R¹⁰ are independently C₁₋₄ alkyl, C₅₋₁₂ aryl, C₇₋₁₃    aralkyl, or C₄₋₁₀ heterocycle (optionally containing one to four    hetero atoms selected from oxygen, a group of the formula: S(→O)_(n)    ⁵ (n⁵ is 0, 1 or 2), a group of the formula: N→O, a group of the    formula: ═N—, and a group of the formula: NR¹¹ (R¹¹ is C₁₋₄ alkyl or    benzyl), or R⁹ and R¹⁰, taken together, may form C₂₋₄ alkylene or    phenylene)

Typical examples of compound (2) used are acetic anhydride, succinicanhydride, propionic anhydride, benzoic anhydride and maleic anhydride.

-   (3) A compound represented by the formula:    (wherein R¹², R¹³, R¹⁴ and R¹⁵ are independently hydrogen, C₁₋₄    alkyl or phenyl, or either of R¹² and R¹³ and either of R¹⁴ and R¹⁵,    taken together, may form C₃₋₁₂ alkylene, and Y³ is oxygen or a group    of the general formula: N—R¹⁶ (R¹⁶ is C₁₋₄ alkyl, C₁₋₄    alkylsulfonyl, C₁₋₅ alkanoyl, C₁₋₅ alkoxycarbonyl or a group of the    general formula: S(→O)_(n) ⁶ (n⁶ is 0, 1 or 2)).

Typical examples of compound (3) used are aziridines, and ethylene oxidederivatives such as ethylene oxide, 2-methyl-1,2-epoxypropane,7-thiabicyclo(4,1,0)heptane, 6-thiabicyclo(3,1,0)hexane,7-oxabicyclo(4,1,0)heptane, 6-oxabicyclo(3,1,0)hexane,7-azabicyclo(4,1,0)heptane, 6-azabicyclo(3,1,0)hexane,7-ethoxycarbonyl-7-azabicyclo(4,1,0)heptane and6-ethoxycarbonyl-6-azabicyclo(3,1,0)hexane.

(4) An α,β-unsaturated carbonyl compound represented by the formula:

(wherein R¹⁷, R¹⁸, R¹⁹ and R²⁰ are independently hydrogen, C₁₋₄ alkyl orphenyl).

Typical examples of compound (4) used are α,β-unsaturated ketonederivatives such as 3-oxo-1,3-diphenyl-1-propene and2-methyl-3-oxo-3-diphenyl-1-propene.

-   (5) A halogenated ethane represented by the formula:    (wherein X⁶, X⁷, X⁸, X⁹, X¹⁰ and X¹¹ are independently hydrogen or    halogen, provided that at least one of X⁶, X⁷ and X⁸ is halogen, and    at lest one of X⁹, X¹⁰ and X¹¹ is halogen).

Typical examples of compound (5) used are halogenated ethanes such ashexachloroethane, hexafluoroethane, 1,1,2,2-tetrabromoethane,1,2-dibromoethane, 1,2-dilodoethane, pentafluoroiodoethane,1,2-dibromo-1,1,2,2-tetrafluoroethane,1,2-dichloro-1,1,2,2-tetrafluroethane,1,1,1-trichloro-2,2,2-trifluoroethane and2,2-trifluoroethane-2,2,1-trichloroethane.

-   (6) A compound represented by the formula:    (wherein X¹² is halogen).

Typical examples of compounds (6) used are succinimides such asN-iodosuccinimide, N-bromosuccinimide and N-chlorosuccinimide.

-   (7) A compound represented by the formula:    (wherein X¹³ is halogen).

Typical examples of compounds (7) used are phthalimides such asN-bromophthalimide and N-chlorophthalimide.

-   (8) A compound represented by the formula:    (wherein R²¹ and R²² are independently C₁₋₄ alkyl or phenyl).

Typical examples of compounds (8) used are disulfide derivatives such asdimethyl disulfide, diethyl disulfide, dipropyl disulfide, dibutyldisulfide and diphenyl disulfide.

-   (9) A compound represented by the formula:    (wherein X¹⁴ is halogen, and R²³ and R²⁴ are independently C₁₋₄    alkyl or phenyl).

Typical examples of compounds (9) used are phosphine derivatives such aschlorodiphenylphosphine, chlorodimethylphosphine, bromodiphenylphosphineand bromodimethylphosphine.

-   (10) A compound represented by the formula:    (wherein X¹⁵ is halogen or phenyl, R²⁵ is C₁₋₄ alkyl, phenyl, C₁₋₄    alkoxy, di-C₁₋₄ alkylamino or C₂₋₅ alkoxycarbonylamino, n⁷ is 0, 1    or 2, and n⁸ is 1, 2 or 3).

Typical examples of compounds (10) used are dimethyl chlorophosphonate,triphenylphosphine oxide and diphenyl chlorophosphonate.

-   (11) A compound represented by the formula:    R²⁶—C≡N  (11)    (wherein R²⁶ is C₁₋₄ alkyl or phenyl).

Typical examples of compounds (11) used are acetonitrile, propionitrile,butyronitrile and benzonitrile.

-   (12) A compound represented by the formula:    (wherein R²⁷ is C₁₋₄ alkyl, di-C₁₋₄ alkylamino, hydroxyl, or C₁₋₄    alkoxy, and R²⁸ and R²⁹ are independently C₁₋₄ alkyl or phenyl).

Typical examples of compounds (12) used are benzophenoneimine andacetone-oxime.

-   (13) A compound represented by the formula:    (wherein R³⁰ and R³¹ are independently C₁₋₄ alkyl or phenyl, or R³⁰    and R³¹, taken together, may form ethylene or propylene,and X¹⁶ is    halogen).

Typical examples of compounds (13) used are compounds represented by thefollowing formulae:

-   (14) A compound represented by the formula:    X¹⁷-M¹    (wherein X¹⁷ is halogen or C₁₋₄ alkoxy and M¹ is copper atom, silver    atom or thallium atom).

Typical examples of compounds (14) used are monovalent metal compoundssuch as cuprous iodide, silver iodide, thallium chloride, thalliumbromide, cuprous chloride, silver chloride, cuprous bromide and silverbromide.

-   (15) A compound represented by the formula:    X¹⁸-M²-X¹⁸    (wherein X¹⁸ is halogen or C₁₋₄ alkoxy, M² is zinc atom, mercury    atom, nickel atom, manganese atom, palladium atom, iron atom or    copper atom).

Typical examples of compounds (15) used are divalent metal compoundssuch as ferrous chloride, zinc chloride, mercuric chloride, cupricchloride, nickel chloride, palladium chloride, manganese chloride,manganese bromide, manganese iodide and manganese fluoride.

-   (16) A compound represented by the formula:    (wherein X¹⁹ is halogen or C₁₋₄ alkoxy, M³ is aluminum atom,    titanium atom, gallium atom, indium atom, vanadium atom, ruthenium    atom, cobalt atom, rare earth atom, scandium atom, yttrium atom or    hafnium atom).

Typical examples of compound (16) used are trivalent metal compoundssuch as zirconium chloride, ferric chloride, ruthenium chloride,ruthenium bromide, ruthenium iodide, cobaltic chloride, scandiumchloride, yttlium chloride, lanthanum chloride, ytterbium chloride,titanium chloride, aluminum chloride, vanadium chloride, vanadiumfluoride, vanadium bromide and gallium chloride.

-   (17) A compound represented by the formula:    (wherein X²⁰ is halogen or C₁₋₄ alkoxy, M⁴ is osmium atom, germanium    atom, titanium atom, zirconium atom, vanadium atom, manganese atom,    ruthenium atom or tin atom).

Typical examples of compounds (17) used are tetravalent metal compoundssuch as germanium chloride, germanium bromide, germanium fluoride,germanium iodide, germanium methoxide, germanium ethoxide, germaniumisopropoxide, titanium chloride, titanium bromide, titanium iodide,titanium fluoride, titanium methoxide, titanium ethoxide, titaniumisopropoxide, titanium butoxide, zirconium chloride, zirconium bromide,zirconium fluoride, zirconium iodide, zirconium methoxide, zirconiumethoxide, zirconium isopropoxide, zirconium butoxide, zirconiumt-butoxide, vanadium chloride, vanadium bromide, vanadium iodide, tinchloride, tin bromide, tin fluoride and tin iodide.

-   (18) A compound represented by the formula:    (wherein R³² and R³³ are independently C₁₋₄ alkyl, X²¹ is halogen or    C₁₋₄ alkoxy, and M⁵ is aluminum atom)

Typical examples of compounds (18) used are aluminum (III) compoundssuch as diethylaluminum chloride, diethylaluminum bromide,diethylaluminum ethoxide, diethylaluminum iodide, diethylaluminumiodide, diisoproylaluminum chloride, dimethylaluminum iodide,dimethylaluminum chloride, dimethylaluminum bromide and dimethylaluminumiodide.

-   (19) A compound of the formula:    (wherein R³⁴ and R³⁵ are independently C₁₋₄ alkyl or phenyl, X²² is    halogen or C₁₋₄ alkoxy, and M⁶ is tin atom).

Typical examples of compounds (19) used are tin (IV) compounds such asdibutyltin dichloride, dibutyltin dibromide, dibutyltin dimethoxide,dimethyltin dibromide, diphenyltin dibromide, dimethyltin dichloride anddiphenyltin dichloride.

-   (20) A compound of the formula:    (wherein X²³ is halogen or C₁₋₄ alkoxy and M⁷ is vanadium atom).

Typical examples of compounds (20) used are vanadium (V) compounds suchas vanadium oxytrichloride, vanadium oxytrifluoride, vanadiumoxytribromide, vanadium oxytriethoxide, vanadium oxytriisopropoxide,vanadium oxytributoxide and vanadium oxytri-t-butoxide.

-   (21) A compound of the formula:    (wherein X²⁴ is trifluoromethanesulfonyloxy or halogen, R³⁶ is C₁₋₄    alkyl or phenyl, and M⁸ is silicon atom)

Typical examples of compounds (21) used are silane derivatives such aschlorotrimethylsilane, chlorotriethylsilane, chlorotributylsilane,chlorotriisoproylsilane, chlorotriphenylsilane, bromotrimethylsilane,bromotriethylsilane, bromotributylsilane, bromotriisopropylsilane,bromotriphenylsilane, trifluoromethanesulfonyloxytrimethylsilane,trifluoromethanesulfonyloxytriethylsilane,trifluorosulfonyloxytributylsilane,trifluoromethanesulfonyloxytriisopropylsilane, and iodotrimethylsilane.

Among compounds (1) to (21) as described above, benzaldehyde,N,N-dimethylformamide or chlorotrimethylsilane is preferable as acompound having an electrophilic group. The substitution of the presentinvention is carried out first by reacting an exchange reagent of thepresent invention with a halogenated compound dissolved in an inertsolvent. More specifically, the halogenated compound dissolved in aninert solvent is added below −5° C. over a period of about 15 minutes toone hour, preferably about 15 minutes to 30 minutes, and then thereaction is usually carried out at −10° C. for about one to two hours.

The inert solvent for dissolution of the halogenated compound can be anysolvents used in halogen-metal exchange reaction with Grignard reagentsand organolithium reagents. Such solvents include, for example, toluene,xylene, tetrahydrofuran, diethyl ether and dimethoxyethane, and amixture thereof.

The halogenated compound dissolved in an inert solvent can be usedusually in approximately 3 to 4 equivalents to the present reagent forexchange reaction.

Then, to the resultant reaction solution is added a compound with anelectrophilic group usually below 0° C. over a period of about 5 to 10minutes. The mixture is allowed to react at the same temperature forabout 30 minutes to one hour.

The compound having an electrophilic group is used usually inapproximately 1 to 3 equivalents, preferably to 1.2 to 2 equivalents, tothe halogenated compound.

When the compound having an electrophilic group is, for example,

(wherein R^(i) and R^(j) are the same or different and are each anoptionally substituted hydrocarbon group), the reaction product istreated with an acid. For example, an acid is added usually below 0° C.and the reaction is carried out at the same temperature for 10 minutesto 2 hours.

The above acid treatment is carried out, for example, at about 0° C. for10 minutes to 2 hours using 1 to 10 equivalents of ammonium chloride,formic acid, trifluoroacetic acid, aqueous citric acid, aqueous aceticacid, hydrochloric acid or dilute sulfuric acid.

The thus obtained compounds by the exchange reaction as described abovecan be purified and isolated, if required, solely or in combination withthe methods known per se in the art, such as chromatography on silicagel or adsorptive resin, liquid chromatography, thin layerchromatography, solvent extraction, andrecrystallization/reprecipitation.

The present exchange reaction is concerned with an improved exchange offunctional groups by means of halogen-metal exchange reaction with knownGrignard reagents and/or organolithium compounds. Therefore, reactionconditions employed in the halogen-metal exchange reaction of Grinardreagents and/or organolithium reagents with electrophilic reagents,including purification of the reaction product except for reactiontemperature, can be adopted as the reaction conditions for each step ofthe present invention.

The process of the present invention relates to a process for producinga compound wherein a halogen atom present in a halogenated compound issubstituted with an electrophilic group, which comprises reacting (i) ahalogenated compound having in the molecule at least one halogen atom orone double or triple bond to which is attached a halogen-substitutedcarbon atom, with (ii) an exchange reagent of the present invention,reacting the resultant product with (iii) a compound having anelectrophilic group, and optionally hydrolyzing the resultant product.

The present process can be carried out according to the aforementionedsubstitution method of this invention.

When the aforementioned compound (V), compound (VI), compound (VII) andcompound (VIII) are employed as the halogenated compound, the reactionproducts include, for example,

-   (1) a compound represented by the formula:    (wherein Z¹ is an electrophilic group and other symbols are each the    same as defined above),-   (2) a compound represented by the formula:    A-(CH₂)_(n) ²-Z²    (wherein Z² is an electrophilic group and other symbols are each the    same as defined above)-   (3) a compound represented by the formula:    (wherein Z³ is an electrophilic group and other symbols are each the    same as defined above), and-   (4) a compound represented by the formula:    (wherein Z⁴ is an electrophilic group and other symbols are each the    same as defined above).

In the above formulae, the electrophilic groups represented by Z¹, Z²,Z³ and Z⁴ are the same as those exemplified above for the compoundshaving an electrophilic group, among which the preferred electrophilicgroup represented by Z¹, Z², Z³ and Z⁴ is —C(═O)H.

The most preferred process of the present invention relates to a processfor preparing 6-bromo-2-formylpyridine or a compound represented by theformula:

(wherein R^(h) is amino protected by pivaloyl, benzyl, phthaloyl ort-butoxycarbonyl), which comprises reacting 2,6-dibromo-pyridine or acompound represented by the formula:

(wherein R^(h) is amino protected by pivaloyl, benzyl, phthaloyl ort-butoxycarbonyl) with a mixture of n-butyl magnesium bromide andn-buityl lithium, or a reaction product from them, reacting theresultant product with N,N-dimethylformamide and hydrolyzing theresultant product with an acid.

Efficiency in the production of compounds whose halogen atom issubstituted with an electrophilic group is remarkably enhanced by use ofthe present exchange reaction for functional groups, i.e. halogen-metalexchange reaction.

Namely, the exchange reaction for functional groups according to thepresent halogen-metal exchange reaction can be carried out at about −10°C. to room temperature, different from extreme low temperatureconditions usually employed, in equimolar amount of reactants to ahalogenated compound, so that cooling equipments for extreme lowtemperature are not required and the amount of the reactants can bereduced, which results in enhancement of efficiency for industrialproduction.

The compounds obtained by the present substitution reaction or theproduction method can be used as a synthetic intermediate forpharmaceuticals or agrochemicals.

More specifically, 6-bromo-2-formylpyridine prepared by the workingexamples hereinafter described is useful as an intermediates for (i)fluorine-containing 1,4-disubstituted-piperidine derivatives whichpossess highly selective muscarine M3 receptor antagonist activityremarkably useful for treatment or prophylaxis of various diseases inrespiratory tract, urinary tract or digestive organ, as disclosed inWO98/05641, (ii) 1-pyridyl naphthalene derivatives which arephosphodiesterase-4 inhibitors useful for treatment of asthma, asdisclosed in Journal of Medicinal Chemistry, Vol. 42, pages 1088-1099(1999) by Tatsuo Ukita, et al., and (iii) 2,6-disubstituted-pyridinederivatives which are leukotriene B4 receptor antagonists useful asanti-inflammatory agents, as disclosed in Tetrahedron Letters Vol. 29,pages 143-146 (1999) by J. Morris, et al, and WO88/05045.5-Bromo-3-formylpyridine is a useful synthetic intermediate forazabicycloaminobenzoic acid derivatives which show integrin antagonisticactivity and are useful for treatment of tumour metastasis, solidtumour, humoral hypercalcemia as disclosed in WO97/08145.4-Bromo-2-fluorobenzaldehyde can be an intermediate for the synthesis ofbenzopyran derivatives possessing LTB4 antagonistic activity useful fortreatment of chronic rheumatoid arthritis, osteoarthritis, eczema,cerebral apoplexy, autoimmune disease or inflammatory diseases includingasthma.

THE BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is hereinafter described in more detail by meansof working examples and reference examples, and these examples are notintended to be limiting to the scope of the invention in any respect.

WORKING EXAMPLE 1 Production of 6-bromo-2-formylpyridine

n-Butyllithium (337 mmol) in 1.52M hexane solution (222 mL) wasdissolved in toluene (500 mL) cooled at −10° C., and n-butylmagnesiumchloride (169 mmol) in 2.00M tetrahydrofuran solution (84.5 ml) wasadded dropwise below −10° C. over a period of 25 minutes. After stirringat −10° C. for one hour, 2,6-dibromopyridine (100 g, 422 mmol) intoluene (1000 mL) was added dropwise to the mixture at an insidetemperature of −10° C. to −6° C. over one hour. The mixture was furtherstirred at −10° C. for 1.5 hours and then N,N-dimethylformamide (65 mL,840 mmol) was added dropwise below −2° C. over 20 minutes. After furtherstirring at 0° C. for one hour, 10% aqueous acetic acid solution (750mL) was added. The mixture was stirred under ice-cooling and the organicphase was separated. The extract was washed with saturated aqueoussodium chloride (25 mL), dried over anhydrous sodium sulfate andconcentrated to give 6-bromo-2-formylpyridine (74.68 g, 98% purity, 95%yield) as a pale yellowish solid.

¹H-NMR (270 MHz, CDCl₃, δ ppm): 7.71-7.80 (m, 2H), 7.93 (m, 1H), 10.01(s, 2H).

WORKING EXAMPLE 2 Production of 1-(6-bromopyridin-2-yl)benzyl alcohol

n-Butylmagnesium chloride (3.49 mmol) in 2.05M tetrahydrofuran solution(1.70 mL) was added to ice-cooled n-butyllithium (7.03 mmol) in 1.45Mhexane solution (4.85 mL) (“Hexanes”, Product of Wako Pure and ChemicalIndustries, Ltd. The solvent was used in the same way in the workingexamples hereinafter described). The mixture was stirred at 0° C. for 15minutes, and then cooled to −10° C. to give a suspension.2,6-Dibromopyridine (2.37 g, 10.0 mmol) in toluene (25 mL) was added tothe suspension below −5° C. over a period of 10 minutes or more. Themixture was stirred at −10° C. for 2 hours, and then benzaldehyde (1.35ml, 13.3 mmol) was added. After stirring at 0° C. for one hour, 1Macetic acid solution (15 mL) was added. The organic phase was separated,and the aqueous phase was extracted twice with ethyl acetate (10 mL).The organic extracts were combined, washed with an aqueous saturatedsolution (10 mL) of sodium chloride, dried over magnesium sulfate andconcentrated under reduced pressure to remove the solvent. The resultantresidue was purified by flash column chromatography on silica gel in adeveloping solvent system of hexane-ethyl acetate (15:1, v/v) to givethe title compound (2.56 g) in 97% yield as a pale yellowish viscousoil.

¹H-NMR (CDCl₃) δ ppm: 4.41 (0.9H, d, J=4.5 Hz), 4.71 (0.1H, br), 5.76(1H, d, J=4.5 Hz), 7.14 (1H, d, J=7.7 Hz), 7.28-7.41 (6H, m), 7.49 (1H,t, J=7.7 Hz).

WORKING EXAMPLE 3 Production of 6-bromo-2-cyanopyridine

n-Butylmagnesium chloride (3.49 mmol) in 2.05M tetrahydrofuran solution(1.70 mL) was added to ice-cooled n-butyllithium (7.03 mmol) in 1.45Mhexane (4.85 mL). The mixture was stirred at 0° C. for 15 minutes, andcooled to −10° C. to give a suspension. 2,6-Dibromopyridine (2.37 g, 10mmol) in toluene (25 mL) was added to the suspension below −5° C. over aperiod of 10 minutes or more. The mixture was stirred at −10° C. for 3hours, and p-toluenesulfonyl cyanide (2.48 g, 13.3 mmol) was added.After the mixture was stirred at 0° C. for 30 minutes, an aqueoussolution (15 mL) of 1M acetic acid was added thereto. The reactionmixture was extracted twice with ethyl acetate (50 mL). The organicextracts combined were washed with an aqueous saturated solution (15 mL)of sodium chloride, dried over magnesium sulfate, and purified by flashcolumn chromatography on silica gel in a developing solvent system ofhexane-ethyl acetate (10:1, v/v) to give the title compound (942 mg,about 51% yield) as orange powder.

WORKING EXAMPLE 4 Production of (6-bromopyridin-2-yl)trimethylsilane

n-Butylmagnesium chloride (4.00 mmol) in 2.00M tetrahydrofuran solution(2.00 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.55Mhexane (5.20 mL). The mixture was stirred at 0° C. for 15 minutes, and2,6-dibromopyridine (2.37 g, 10.0 mmol) in toluene (25 mL) was addedthereto below 10° C. over a period of 10 minutes or more. The resultantsuspension was stirred at 0° C. for one hour, and chlorotrimethylsilane(13 mmol, 1.65 mL)) was added thereto. After the mixture was stirred at0° C. for one hour and at room temperature for 1.5 hours, an aqueoussolution (20 mL) of 1M acetic acid was added thereto. The reactionmixture was extracted twice with ethyl acetate (50 mL). The organicphase was separated, washed with water (10 mL), dried over magnesiumsulfate, and concentrated under reduced pressure to give a residue. Theresidue was purified by flash column chromatography on silica gel in adeveloping solvent system of hexane-ethyl acetate (20:1, v/v) to givethe title compound (881 mg, about 38% yield) as colorless powder.

¹H-NMR (CDCl₃) δ ppm: 0.32 (9H, s), 7.37 (1H, dd, J=3.2, 6.0 Hz), 7.42(1H, dd, J=3.0, 3.2 Hz), 7.43 (1H, d, J=3.0, 3.8 Hz).

WORKING EXAMPLE 5 Production of 6-bromo-3-formylpyridine

n-Butylmagnesium chloride (4.00 mmol) in 2.00M tetrahydrofuran solution(2.00 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.55Mhexane (20 mL). The mixture was stirred at 0° C. for 15 minutes to givea suspension. The suspension was added to a mixture of toluene (15 mL)and tetrahydrofuran (10 mL) containing 2,5-dibromopyridine (2.37 g, 10.0mmol) over a period of 10 minutes or more while keeping the temperaturebelow −5° C. to give a dark orange solution. The solution was stirred at0° C. for 1.25 hours and then at 20° C. for one hour. The solution wascooled to 0° C., and N,N-dimethylformamide (1.0 mL, 13 mmol) was addedthereto. After the mixture was stirred at 0° C. for 30 minutes, 1Maqueous acetic acid solution (20 mL) was added. The organic phase wasseparated, and the aqueous phase was extracted twice with ethyl acetate(10 mL). The organic phases were combined, washed with saturated aqueoussodium chloride (15 mL), dried over magnesium sulfate and concentratedunder reduced pressure to remove the solvent. The resultant residue waspurified by flash column chromatography on silica gel in a developingsolvent system of hexane-ethyl acetate (20:1, v/v) to give the titlecompound (1.229 g, 66% yield) as a colorless solid.

¹H-NMR (CDCl₃) δ ppm: 7.69 (1H, d, J=8.4 Hz), 8.02 (1H, dd, J=2.4, 8.4Hz), 8.84 (1H, d, J=2.4 Hz), 10.10 (1H, s).

WORKING EXAMPLE 6 Production of 5-bromo-3-formylpyridine

n-Butylmagnesium chloride (4.00 mmol) in 2.00M tetrahydrofuran solution(2.00 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.55Mhexane (5.20 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. The suspension was added to a mixture of toluene (15mL) and tetrahydrofuran (10 mL) containing 2,5-dibromo-pyridine (2.37 g,10.0 mmol) over a period of 10 minutes or more while keeping thetemperature below 5° C. to give an orange solution. The solution wasstirred at 0° C. for one hour, and N,N-dimethylformamide (1.0 mL, 13mmol)was added thereto. The resultant suspension was stirred at roomtemperature for 30 minutes, and tetrahydrofuran (10 mL) was added,followed by further stirring at room temperature for 30 minutes. Afteraddition of 1M aqueous acetic acid (20 mL) to the suspension, theorganic phase was separated, and the aqueous phase was extracted withtoluene (20 mL). The organic phase and the toluene extract werecombined, washed with an aqueous sodium chloride saturated solution (15mL), dried over magnesium sulfate and concentrated under reducedpressure to remove the solvent. The resultant residue was purified byflash column chromatography on silica gel in a developing solvent systemof hexane-ethyl acetate (10:1, v/v) to give the title compound (1.062 g,57% yield) as a colorless solid.

¹H-NMR (CDCl₃) δ ppm: 8.31 (1H, dd, J=1.5, 2.2 Hz), 8.92 (1H, d, J=2.2Hz), 9.00 (1H, d, J=1.5 Hz), 10.09 (1H, s).

WORKING EXAMPLE 7 Production of 1-(5-bromopyridin-3-yl)benzyl alcohol

n-Butylmagnesium chloride (3.49 mmol) in 2.05M tetrahydrofuran solution(1.70 mL) was added to ice-cooled n-butyllithium (6.99 mmol) in 1.52Mhexane (4.60 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. The suspension was added to a tetrahydrofuransolution (25 mL) containing 3,5-dibromopyridine (2.37 g, 10.0 mmol) overa period of 10 minutes or more, while keeping the temperature below −5°C., to give an orange suspension. The suspension was stirred at −10° C.for one hour, and benzaldehyde (1.35 mL, 13.3 mmol) was added thereto.The resultant mixture was stirred at 0° C. for 30 minutes, and then 1Macetic acid solution (15 mL) was added. The reaction mixture wasextracted twice with ethyl acetate (20 mL). The organic extracts werecombined, washed with saturated aqueous sodium chloride (10 mL), driedover magnesium sulfate and was purified by flash column chromatographyon silica gel in a developing solvent system of hexane-ethyl acetate(5:1, v/v) to give the title compound (1.647 g, 59% yield) as acolorless oil.

¹H-NMR (CDCl₃) δ ppm: 2.57 (1H, br), 5.85 (1H, s), 7.30-7.41 (5H, m),7.89 (1H, dt, J=0.7, 2.2), 8.51 (1H, s), 8.55 (1H, s).

WORKING EXAMPLE 8 Production of 4-bromobenzaldehyde

n-Butylmagnesium chloride (4.00 mmol) in 2.00M tetrahydrofuran solution(2.00 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.55Mhexane (5.20 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. To the suspension was added dropwise a toluenesolution (25 mL) containing 1,4-dibromobenzene (2.36 g, 10 mmol) over aperiod of 15 minutes, while keeping the temperature below 5° C., to givea white suspension. After the suspension was stirred at 0° C. for 5hours, N,N-dimethylformamide (1.0 mL, 13 mmol) was added thereto. Theresultant mixture was stirred at 0° C. for 30 minutes, and 10% aceticacid solution (20 mL) was added. The organic phase was separated and theaqueous phase was extracted with toluene (20 mL). The organic layerswere combined, washed with water (20 mL), and dried over magnesiumsulfate. Toluene was added to the solution to a volume of 100 mL. Thesolution (98 ml) was purified by flash column chromatography on silicagel in a developing solvent system of hexane-ethyl acetate (30:1, v/v)to give the title compound (1.507 g, 81% yield) as a colorlesscrystalline solid.

¹H-NMR (CDCl₃) δ ppm: 7.67-7.77 (4H, AB-like m), 9.98 (1H, s).

WORKING EXAMPLE 9 Production of 3-bromobenzaldehyde

n-Butylmagnesium chloride (4.00 mmol) in 2.00M tetrahydrofuran solution(2.00 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.55Mhexane (5.20 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. To the suspension was added dropwise a toluenesolution (25 mL) containing 1,3-dibromobenzene (2.36 g, 10.0 mmol),while keeping the temperature below 5° C., over a period of 15 minutes,thereby to give a suspension. The suspension was stirred at 0° C. for 5hours, and then N,N-dimethylformamide (1.0 mL, 13 mmol) was addedthereto. The resultant mixture was stirred at 0° C. for 30 minutes, and10% aqueous acetic acid (20 mL) was added. The reaction mixture wasextracted twice with toluene (20 mL). The organic extracts werecombined, washed with water (20 mL), and dried over magnesium sulfate.Toluene was added to the solution to a volume of 85 mL. The solution (83ml) was purified by flash column chromatography on silica gel in adeveloping solvent system of hexane-ethyl acetate (25:1, v/v) to givethe title compound (1.446 g, 78% yield) as a pale yellowish crystallinesolid.

¹H-NMR (CDCl₃) δ ppm: 7.43 (1H, t, J=2.0), 7.76 (1H, ddd, J=1.3, 2.0,7.9), 7.81 (dt, J=1.3, 7.9), 8.02 (1H, t, J=2.0), 9.97 (1H, s).

WORKING EXAMPLE 10 Production of 4-bromo-2-fluorobenzaldehyde

n-Butylmagnesium chloride (3.49 mmol) in 2.05M tetrahydrofuran solution(1.70 mL) was added to ice-cooled n-butyllithium (8.06 mmol) in 1.45Mhexane (4.85 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. To the suspension was added dropwise a toluenesolution (25 mL) containing ice-cooled 1,4-dibromo-2-fluorobenzene (2.54g, 10.0 mmol) over a period of 10 minutes, while keeping the temperaturebelow 5° C. The resultant yellowish suspension was stirred at 0° C. forone hour, and N,N-dimethylformamide (1.0 mL, 13 mmol) was added thereto.The mixture was stirred at 0° C. for 30 minutes, and 1M aqueous aceticacid solution (15 mL) was added. The reaction mixture was extractedtwice with ethyl acetate (15 mL). The organic extracts were combined,and 20% aqueous sodium hydrogen sulfite solution (5 mL) was added atroom temperature. The mixture was stirred vigorously at room temperaturefor one hour. The aqueous phase was separated, washed with ethyl acetate(15 mL), adjusted to pH 10 with 6N sodium hydroxide solution, andextracted twice with ethyl acetate (25 ml). The organic extracts werecombined, washed successively with aqueous ammonium chloride saturatedsolution (10 mL) and saturated aqueous sodium chloride (10 mL), driedover magnesium sulfate, and concentrated to dryness under reducedpressure to give the title compound (1.666 g, 82% yield) as an almostcolorless crystalline solid.

¹H-NMR (CDCl₃) δ ppm: 7.40 (1H, dd, J=1.7, 9.7), 7.45 (1H, dddd, J=1.7,1.7, 1.7, 8.3), 7.75 (1H, dd, J=7.4, 8.3), 10.31 (1H, s).

WORKING EXAMPLE 11 Production of 5-bromo-2-thiophenecarboxyaldehyde

n-Butylmagnesium chloride (3.50 mmol) in 2.01M tetrahydrofuran solution(1.74 mL) was added to ice-cooled n-butyllithium (7.00 mmol) in 1.61Mhexane (4.35 mL). The mixture was stirred at 0° C. for 15 minutes togive a suspension. To the suspension was added dropwise a toluenesolution (25 mL) containing 2, 5-dibromothiophene (2.55 g, content 95w/w %, 10.0 mmol) over a period of 10 minutes, while keeping thetemperature below −5° C. The resultant pale yellowish suspension wasstirred at −10° C. for 3 hours, and N,N-dimethylformamide (1.0 mL, 13mmol) was added. The mixture was stirred at 0° C. for 30 minutes, and 1Naqueous acetic acid solution (15 mL) was added. The reaction mixture wasextracted twice with ethyl acetate (15 mL). The organic extracts thusobtained were combined, washed with water (10 mL), dried over magnesiumsulfate, and concentrated under reduced pressure to remove the solvent.The resultant residue was purified by flash column chromatography onsilica gel in a developing solvent system of hexane-ethyl acetate (20:1,v/v) to give the title compound (1.387 g, 73% yield) as a yellow oil.

¹H-NMR (CDCl₃) δ ppm: 7.20 (1H, d, J=4.0), 7.52 (1H, d, J=4.0), 9.78(1H, s).

REFERENCE EXAMPLE Production of 6-bromo-2-formylpyridine

A solution (650 mL) of 2,6-dibromopyridine (100 g, 422 mmol) intetrahydrofuran was added dropwise to a tetrahydrofuran solution (250mL) of butyllithium (as 1.57M hexane solution 282 mL, 435 mmol) over aperiod of 43 minutes, while keeping the temperature below −70° C. Themixture was stirred at −73° C. for 20 minutes, and N,N-dimethylformamide(98 mL, 1266 mmol) was added dropwise over a period of 25 minutes whilekeeping the temperature below −70° C. After further stirring for 20minutes, the reaction solution was analyzed to indicate thatphysicochemical data of the product was identical to those as reportedin the known literature, i.e. Journal of Inorganic Chemistry, Vol. 10,pages 2472-2478 (1971) by J. E. Parks, et al., and identified as6-bromo-2-formylpyridine.

INDUSTRIAL APPLICABILITY

By use of the present reagents for exchange reaction for functionalgroups, a halogen atom in halogenated compounds can be efficientlysubstituted with an electrophilic group, and synthetic intermediatescommonly used in the field of chemical industries, agrochemicals andpharmaceuticals can be prepared more efficiently.

1. A process for exchanging a halogen atom present in a halogenatedcompound for an electrophilic group, which comprises: reacting (i) (1) ahalogenated compound represented by the formula:

wherein Y¹ is a divalent organic residue, Y² is a monovalent organicresidue, or Y¹ and Y², when taken together, represent a trivalentorganic residue, X² is a halogen atom, and n¹ is 0 or 1, or (2) ahalogenated compound represented by the formula:A-(CH₂)n²—X³  (VI) wherein A is an optionally substituted aromatic ring,n² is 0 or 1 and X³ is a halogen atom, with (ii) an exchange reagentwhich comprises a mixture of (A) (1) a magnesium compound represented bythe formula:R¹—Mg—X¹  (I) wherein R¹ is a halogen atom or an optionally substitutedhydrocarbon residue, and X¹ is a halogen atom or (2) a member selectedfrom the group consisting of diethylmagnesium, dipropylmagnesium,diisopropylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium,di-tert-butylmagnesium, diphenylmagnesium, divinylmagnesium,diallylmagnesium, di(2-furyl)magnesium, di(3-furyl)magnesium,di(2-thienyl)magnesium, di(3-thienyl)magnesium and dibenzylmagnesium and(B) an organolithium compound represented by the formula:R²—Li  (II) wherein R² is an optionally substituted hydrocarbon residue,or a reaction product from (A) and (B), reacting the resultant productwith (iii) a compound having an electrophilic group, and optionallytreating the resultant product with an acid.
 2. A process for exchanginga halogen atom present in a halogenated compound for an electrophilicgroup, which comprises: reacting (i) a halogenated compound representedby the formula:

wherein X⁴ is a halogen atom, R³ is a hydrogen atom, a protected aminogroup, an optionally substituted hydrocarbon group, an optionallysubstituted hydrocarbon-oxy group or a halogen atom, and n is 1 or 2,with (ii) an exchange reagent which comprises a mixture of (A) (1) amagnesium compound represented by the formula:R¹—Mg—X¹  (I) wherein R¹ is a halogen atom or an optionally substitutedhydrocarbon residue, and X¹ is a halogen atom or (2) a member selectedfrom the group consisting of diethylmagnesium, dipropylmagnesium,diisopropylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium,di-tert-butylmagnesium, diphenylmagnesium, divinylmagnesium,diallylmagnesium, di(2-furyl)magnesium, di(3-furyl)magnesium,di(2-thienyl)magnesium, di(3-thienyl)magnesium and dibenzylmagnesium and(B) an organolithium compound represented by the formula:R²—Li  (II) wherein R² is an optionally substituted hydrocarbon residue,or a reaction product from (A) and (B), reacting the resultant productwith (iii) a compound having an electrophilic group, and optionallytreating the resultant product with an acid.
 3. A process for exchanginga halogen atom present in a halogenated compound for an electrophilicgroup, which comprises: reacting (i) a halogenated compound representedby the formula:

wherein R⁴ is a hydrogen atom, a protected amino group, an optionallysubstituted hydrocarbon group, an optionally substituted hydrocarbon-oxygroup or a halogen atom, and X⁵ is a halogen atom, with (ii) an exchangereagent which comprises a mixture of (A) (1) a magnesium compoundrepresented by the formula:R¹—Mg—X¹  (I) wherein R¹ is a halogen atom or an optionally substitutedhydrocarbon residue, and X¹ is a halogen atom or (2) a member selectedfrom the group consisting of diethylmagnesium, dipropylmagnesium,diisopropylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium,di-tert-butylmagnesium, diphenylmagnesium, divinylmagnesium,diallylmagnesium, di(2-furyl)magnesium, di(3-furyl)magnesium,di(2-thienyl)magnesium, di(3-thienyl)magnesium and dibenzylmagnesium and(B) an organolithium compound represented by the formula:R²—Li (II) wherein R² is an optionally substituted hydrocarbon residue,or a reaction product from (A) and (B), reacting the resultant productwith (iii) a compound having an electrophilic group, and optionallytreating the resultant product with an acid.
 4. The process according toany one of claims 1 to 3, wherein the compound having an electrophilicgroup is benzaldehyde, chlorotrimethylsilane or N,N-dimethylformamide.5. The process according to any one of claims 1 to 3, wherein themagnesium compound represented by the formula (I) is n-butylmagnesiumbromide or n-butylmagnesium chloride, and the organolithium compoundrepresented by the formula (II) is n-butyllithium.
 6. The processaccording to any one of claims 1 to 3, wherein the reaction product from(A) and (B) is (1) a compound represented by the formula:(R^(a)R^(b)R^(c)Mg)⁻.Li⁺  (III) wherein R^(a), R^(b) and R^(c) are thesame or different and are each an optionally substituted hydrocarbonresidue, or (2) a compound represented by the formula:(R^(d)R^(e)R^(f)R^(g)Mg)²⁻.2Li⁺  (IV) wherein R^(d), R^(e), R^(f) andR^(g) are the same or different and are each an optionally substitutedhydrocarbon residue.
 7. The process according to claim 6, wherein R^(a),R^(b) and R^(c) are each n-butyl group.
 8. The process according toclaim 6, wherein R^(d), R^(e), R^(f) and R^(g) are each n-butyl group.9. The process according to claim 6, wherein the compound represented bythe formula (III) is tri-n-butylmagnesium lithium, and the compoundrepresented by the formula (IV) is tetra-n-butylmagnesium dilithium. 10.The process according to any one of claims 1 to 3, which comprisesreacting, as the halogenated compound, 2-6-dibromopyridine or a compoundrepresented by the formula:

wherein R^(e) is a protected amino group, with, as the exchange reagent,a mixture of n-butylmagnesium chloride and n-butyllithium, or a reactionproduct thereof, reacting the product with N,N-dimethylformamide, andtreating the product with an acid, to obtain 6-bromo-2-formylpyridine ora compound represented by the formula:

wherein R^(e) is a protected amino group.
 11. The process according toany one of claims 1 to 3, wherein the reagent (A) isdi-n-butylmagnesium.